MEASUREMENT OF HUMAN TISSUE-TYPE PLASMINOGEN-ACTIVATOR BY A 2-SITE IMMUNORADIOMETRIC ASSAY

Abstract

A 2-site immunoradiometric assay for human extrinsic (tissue-type) plasminogen activator was developed by using rabbit antibodies raised against plasminogen activator purified from human melanoma cell culture fluid. Samples of 100 .mu.l containing 1-100 ng/ml plasminogen activator were incubated in the wells of polyvinyl chloride microtiter plates coated with antibody. The amount of bound extrinsic plasminogen activator was quantitated by the subsequent binding of 125I-labeled affinospecific antibody. The mean level of plasma samples taken at rest was 6.6 .+-. 2.9 ng/ml (n = 54). This level increased .apprx. 3-fold exhaustive physical exercise, venous occlusion or infusion of DDAVP [1-deamino-8-D-arginine vasopressin]. Extrinsic plasminogen activator in plasma is composed of a fibrin-adsorbable and active component (1.9 .+-. 1.1 ng/ml, n = 54, in resting conditions) and an inactive component that does not bind to a fibrin clot (probably extrinsic plasminogen activator-proteinase inhibitor complexes). The fibrin-adsorbable fraction increased .apprx. 5- to 8-fold after physical exercise, venous occlusion or DDAVP injections. Potential applications of the immunoradiometric assay are illustrated by the measurement of extrinsic plasminogen activator in different tissue extracts, body fluids, cell culture fluids and oocyte translation products after injection with mRNA for plasminogen activator.